Microfluidic devices are devices that contain structures that handle fluids on a small scale. Typically, a microfluidic device operates on a sub-millimeter scale and handles micro-liters, nano-liters, or smaller quantities of fluids. In microfluidic devices, a major fouling mechanism is trapped air, or bubbles, inside the micro-structure. This can be particularly problematic when using a thermoplastic material to create the microfluidic structure, as the gas permeability of thermoplastics is very low.
In order to avoid fouling by trapped air, previous microfluidic structures use either simple straight channel or branched channel designs with thermoplastic materials, or else manufacture the device using high gas permeability materials such as elastomers. However, simple designs limit possible functionality of the microfluidic device, and elastomeric materials are both difficult and expensive to manufacture, particularly at scale.
One application of microfluidic structures is in digital polymerase chain reaction (dPCR). dPCR dilutes a nucleic acid sample down to one or less nucleic acid template in each partition of a microfluidic structure providing an array of many partitions, and performs a PCR reaction across the array. By counting the partitions in which the template was successfully PCR amplified and applying Poisson statistics to the result, the target nucleic acid is quantified. Unlike the popular quantitative real-time PCR (qPCR) where templates are quantified by comparing the rate of PCR amplification of an unknown sample to the rate for a set of known qPCR standards, dPCR has proven to exhibit higher sensitivity, better precision and greater reproducibility.
For genomic researchers and clinicians, dPCR is particularly powerful in rare mutation detection, quantifying copy number variants, and Next Gen Sequencing library quantification. The potential use in clinical settings for liquid biopsy with cell free DNA and viral load quantification further increases the value of dPCR technology. Existing dPCR solutions have used elastomeric valve arrays, silicon through-hole approaches, and microfluidic encapsulation of droplets in oil. Despite the growing number of available dPCR platforms, dPCR has been at a disadvantage when compared to the older qPCR technology which relies on counting the number of PCR amplification cycles. The combination of throughput, ease of use, performance and cost are the major barriers for gaining adoption in the market for dPCR.